On Fri, 21 Oct 2005 14:37:54 GMT, chuck wrote:

There are a couple of ways to do this.

1. Use resistive pads at the outputs of the two radios and a resistive
summation circuit to feed a separate amplifier which then feeds the
single speaker.

Not a great idea in that you'll want to be putting something like a 3-4 ohm pad
in there. AND if you have a 20 watt output (not likely into 8 ohms) you'll want
to use a 20 watt resistors. (atually 20watt resistors will get pretty damn hot!)
Not to mention you'll be loosing most your output power in heat. Pretty poor
solution. - If you don't care about the loss then use some like 3 ohms for the
resistors. Assuming the amps are rated to drive no less than 4 ohms this will
keep you safe if the horn is 4 or 8. Seems like a rather silly solution with
this much power loss. Best you'll ever get is less than 3 watts to the speaker
at full amp output.


2. Use a stereo-to-monaural isolation transformer backwards. Each radio
feeds one stereo input and the monaural winding feeds your single speaker.

Except for the DC component this is no different than just tying the leads
together. The transformer provides DC isolation not AC isolation. The outputs
from the two radios are likely ALREADY isolated in terms of the DC. This is not
a option.